enabling gtags auto tag completion in Global compatible modes

(require 'gtags)
(defun gtags-root-dir ()
  "Returns GTAGS root directory or nil if doesn't exist."
  (with-temp-buffer
    (if (zerop (call-process "global" nil t nil "-pr"))
        (buffer-substring (point-min) (1- (point-max)))
      nil)))
(defun gtags-update ()
  "Make GTAGS incremental update"
  (message "updating GLOBAL tags using gtags -i ..") 
  (call-process "gtags" nil nil nil "-i -f gtags.files")
  (gtags-make-complete-list))

(defun gtags-update-global ()
  "Make GTAGS incremental update"
  (message "updating GLOBAL tags!!")  
  (call-process "global" nil nil nil "-u")
  (gtags-make-complete-list))

(defun gtags-update-hook ()
  (when (gtags-root-dir)
    (when (memq major-mode (list 'php-mode 'c-mode 'org-mode 'javascript-mode 'js-mode 'emacs-lisp-mode))
      (progn (message "global root : %s" (gtags-root-dir))(gtags-update-global)))))
(add-hook 'after-save-hook 'gtags-update-hook)

(defadvice gtags-find-tag (before gtags-make-complete-list activate)
  "Make Global completion tags" (unless gtags-complete-list (gtags-make-complete-list)))

(add-hook 'php-mode-hook '(lambda () (gtags-mode t)))
(add-hook 'c-mode-hook '(lambda () (gtags-mode t)))

(provide 'rgr-gtags)

--
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